Source Analysis During the Early Late Triassic in Ordos Basin

Based on directions of palaeo-flow, mineral combination characteristic and REE characteristic in Ordos Basin, directions of palaeo-flow of the early Yanchang Formation comesfrom circum to center, and five source directions can be found, which are northeast, ea st, south, southwest and northwest directions. The mainsource directions are northeast, southwest and northwest directions. The northeast source obviously dominates, and influencearea of south source is narrower. The main parent rock of the early Yanchang Formation is complex metamorphic rock of A rchean and metavolcanic rock-sed imentary rock system. The northeast source comes from the sustained source offered by the old Yinshan and the Daqingshan, so delta deposit develops grossly. The south source mainly comes from gneiss and granide of early Palaeozoic in the Qinling and Qilianshan fold orogenic zone, the characteristics of which are close to the provenance and sediment size obviously wider than the northeast source.